



A Network of Biologically Inspired Rectified Spectral Units (ReSUs) Learns Hierarchical Features Without Error Backpropagation | "Brain-like artificial neurons that teach themselves to recognize increasingly complex patterns by predicting the future from the past, without needing training data."
##Abstract:
>We introduce a biologically inspired, multilayer neural architecture composed of Rectified Spectral Units (ReSUs). Each ReSU projects a recent window of its input history onto a canonical direction obtained via canonical correlation analysis (CCA) of previously observed past-future input pairs, and then rectifies either its positive or negative component. By encoding canonical directions in synaptic weights and temporal filters, ReSUs implement a local, self-supervised algorithm for progressively constructing increasingly complex features. > >To evaluate both computational power and biological fidelity, we trained a two-layer ReSU network in a self-supervised regime on translating natural scenes. First-layer units, each driven by a single pixel, developed temporal filters resembling those of Drosophila post-photoreceptor neurons (L1/L2 and L3), including their empirically observed adaptation to signal-to-noise ratio (SNR). Second-layer units, which pooled spatially over the first layer, became direction-selective -- analogous to T4 motion-detecting cells -- with learned synaptic weight patterns approximating those derived from connectomic reconstructions. Together, these results suggest that ReSUs offer: >- (i) a principled framework for modeling sensory circuits and >- (ii) a biologically grounded, backpropagation-free paradigm for constructing deep self-supervised neural networks.
##Layman's Explanation:
Your brain learns to see without anyone telling it the right answers. This paper tries to build artificial neurons that work the same way.
Standard AI neurons (ReLUs) just add up inputs at one instant and ignore timing. Real neurons track patterns over time. The authors propose a new unit called a ReSU (Rectified Spectral Unit) that looks at a window of recent input history, finds the pattern most useful for predicting what comes next using a statistical method called canonical correlation analysis, and then outputs only the positive or negative part of that pattern.
They tested a two-layer ReSU network on natural images sliding across a simulated eye, mimicking how a fruit fly sees motion. Without any labeled training data or backpropagation, the first layer spontaneously developed filters matching real fly neurons (L1, L2, L3), and the second layer became direction-selective like the fly's motion-detecting T4 cells. The learned connection weights even resembled those mapped from actual fly brain wiring diagrams.
The core claim is that a single principle (maximize the information your past observations give you about the future, then split positive and negative responses across separate neurons) can explain how biological circuits self-organize into hierarchical feature detectors, and could eventually replace backpropagation in deep networks.
######Link to the Paper: https://arxiv.org/pdf/2512.23146
######Link to the Code: https://github.com/ShawnQin/ReSU